Q: A sample of water (mass = 100 g, $$ c = 4.18 \text{ J/g} \cdot \text{K} ) is $$heated from 25°C to 75°C. How much heat is absorbed by the water?

$$ q = 100 \times 4.18 \times (75 - 25) = 20,900 \text{ J} $$

Question 1

Which of the following best describes the difference between kinetic energy and potential energy in a chemical system?

Accepted Answer

Kinetic energy is the energy of motion of particles, while potential energy is the energy stored due to position or arrangement.

Question 2

Which equation correctly represents the First Law of Thermodynamics for a closed system?

Accepted Answer

$$ \Delta E = q + w $$

Question 3

A student mixes two solutions in a coffee-cup calorimeter and observes the temperature of the mixture increases. Which statement is correct regarding the reaction?

Accepted Answer

The reaction is exothermic because heat is released to the surroundings.

Question 4

Which of the following is the correct formula to calculate the heat absorbed or released by a substance, given its mass, specific heat capacity, and temperature change?

Accepted Answer

$$ q = m c \Delta T $$

Question 5

In a bomb calorimeter, which of the following statements is true regarding the measurement of heat?

Accepted Answer

The heat measured corresponds to the change in internal energy at constant volume.

Question 6

Which of the following best defines enthalpy ($$ H ) in $$terms of internal energy ($$ E $$), pressure ($$ P $$), and volume ($$ V $$)?

Accepted Answer

$$ H = E + PV $$

Question 7

A chemical reaction has $$ \Delta H = -150 	ext{ kJ} . $$Which statement is correct?

Accepted Answer

The reaction is exothermic and releases 150 kJ of heat.

Question 8

Which of the following equations correctly relates work ($$ w ) $$done by a gas at constant pressure to the change in volume ($$ \Delta V $$)?

Accepted Answer

$$ w = -P \Delta V $$

Question 9

A sample of water (mass = 100 g, $$ c = 4.18 	ext{ J/g} \cdot 	ext{K} ) is $$heated from 25°C to 75°C. How much heat is absorbed by the water?

Accepted Answer

$$ q = 100 	imes 4.18 	imes (75 - 25) = 20,900 	ext{ J} $$

Question 10

Which statement best explains why constant-volume calorimetry measures the change in internal energy ($$ \Delta E ) $$rather than enthalpy ($$ \Delta H $$)?

Accepted Answer

Because no work is done by expansion or compression at constant volume.

Question 11

Which of the following is NOT a correct statement about the system and surroundings in thermodynamics?

Accepted Answer

The system and surroundings cannot exchange energy.

Question 12

A reaction is carried out in a coffee-cup calorimeter at constant pressure. Which quantity does the heat measured correspond to?

Accepted Answer

Change in enthalpy ($$ \Delta H )$$

Question 13

Which of the following best describes an endothermic reaction?

Accepted Answer

A reaction in which heat is absorbed from the surroundings.

Question 14

If a chemical reaction is performed in a bomb calorimeter and the temperature of the calorimeter increases, what can be concluded?

Accepted Answer

The reaction is exothermic and releases heat to the surroundings.

Question 15

Which of the following is the correct equation for calculating the heat capacity ($$ C ) of a $$substance?

Accepted Answer

$$ C = \dfrac{q}{\Delta T} $$

Question 16

A reaction has $$ \Delta H = +85 	ext{ kJ} . $$Which of the following is true?

Accepted Answer

The reaction is endothermic and absorbs 85 kJ of heat.

Question 17

Which of the following best describes the function of a calorimeter in chemical experiments?

Accepted Answer

To measure the heat exchanged between the system and surroundings.

Question 18

Which of the following is a correct statement about specific heat capacity?

Accepted Answer

It is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Question 19

A chemical reaction is performed at constant pressure and releases 200 kJ of heat. What is the value of $$ \Delta H $$ for the reaction?

Accepted Answer

$$ \Delta H = -200 	ext{ kJ} $$

Chem - chapter 9 study guide

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